• Volume 40,Issue 1,2018 Table of Contents
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    • >地震工程
    • Dynamic Fracture of Heavy Haul Railway Tunnels with Cracks Under Seismic Loads

      2018, 40(1):1-5. DOI: 10.3969/j.issn.1000-0844.2018.01.001

      Abstract (1011) HTML (0) PDF 2.00 M (1066) Comment (0) Favorites

      Abstract:Tunnel damage is aggravated by the interaction between cracks and earthquake loading. Thus, the study of the dynamic fracture of tunnel lining with cracks under earthquake loading is of great importance. In this study, the correctness of the simulated results was calculated by the two-dimensional finite element method, while the dynamic stress intensity factors for a plate with a stationary crack under dynamic loads were first computed by the interaction integral method. The numerical results were then compared to the analytical solutions, with whom they were found to be in good agreement. The computational results showed that the interaction integral method can be used to obtain accurate dynamic stress intensity factors for cracked structures under dynamic loads. Subsequently, the method was used to calculate the dynamic stress intensity factors and the bearing capacity safety factors for the lining of heavy haul railway tunnels with cracks. The Xixian heavy haul railway tunnel located in the south-central area of the Shanxi Province was considered as a case study, with additional consideration given to twelve working conditions. A 2D finite element model was established in order to compute the dynamic fracture of a tunnel with cracks under earthquake loading. The results showed that under the seismic loads, the dynamic stress intensity factors of mode I cracks controlled the safety of the tunnel structure. Thereby, if the length of the crack was greater than a certain value, the tunnel was assessed as dangerous.

    • A Retrofit Cost Estimation Model of Masonry Structures Based on the Multiple Linear Regression Method

      2018, 40(1):6-13. DOI: 10.3969/j.issn.1000-0844.2018.01.006

      Abstract (850) HTML (0) PDF 1.04 M (1031) Comment (0) Favorites

      Abstract:In this paper, retrofit costs and relative building parameters of masonry structures in Shaanxi, Shanxi, and Sichuan Provinces were collected, to enable a retrofit cost estimation model for masonry structure buildings to be developed. A regression and validation database, including the retrofit cost estimation models of 35 buildings, was built, and the building parameters which influence retrofit costs analyzed. Then, based on the multiple linear regression method, four models were established using the existing retrofit data with SPSS analysis software. After evaluating the four models according to their corresponding evaluation criteria, an optimal rapid estimation model for the retrofit cost of masonry structures was proposed and verified. The results show that the regression model meets the precision requirements and could be valuable in practical engineering.

    • Evaluation of Earthquake Damage and Anti-destruction Ability of Concrete High-rise Building Structures

      2018, 40(1):14-19,47. DOI: 10.3969/j.issn.1000-0844.2018.01.014

      Abstract (1021) HTML (0) PDF 1.10 M (1169) Comment (0) Favorites

      Abstract:In previous studies, evaluations of earthquake damage and anti-destruction ability of concrete high-rise buildings based on the static nonlinear evaluation method and structural damage assessment model do not consider the damage development of structures under an earthquake; thus, the evaluation results often differ from reality. Therefore, this paper proposes an evaluation method of earthquake damage and anti-destruction ability of concrete high-rise buildings based on component performance. By using the strength and ductility method, the performance of concrete high-rise buildings under strong earthquakes can be exactly described based on the strength and deformation of the building. Based on the structure performance and the analysis of the collapse limit state of high-rise buildings subjected to various seismic waves, the collapse resistant capacity ratio of structure is set up with the incremental dynamic analysis (IDA) method. According to the ratio, the evaluation process of earthquake damage and the anti-destruction ability of concrete high-rise buildings based on component performance can be obtained. The experimental results confirm that the proposed method can be used to exactly describe the earthquake damage and anti-destruction ability of concrete high-rise buildings.

    • Optimized Evaluation Analysis of Seismic Collapse Capacity of Public Buildings

      2018, 40(1):20-25. DOI: 10.3969/j.issn.1000-0844.2018.01.020

      Abstract (825) HTML (0) PDF 3.21 M (1183) Comment (0) Favorites

      Abstract:In the past, using the modal incremental dynamic method to evaluate the seismic collapse capacity of public buildings did not accurately reflect the earthquake collapse resistance of public buildings, thus gaining poor economic benefits. In this study, a new and optimized evaluation method of determining the seismic collapse capacity of public buildings is proposed and used to analyze the overall performances of public buildings. Then, the relationship among the overall structure of public buildings, substructures, and components is summarized. The overall evaluation on the public building is fulfilled by evaluating the damage situation of components. Based on the seismic damage interval of public buildings, the optimized evaluation on seismic collapse capacity of public buildings are finished with the proposed method, and the damage indices of the seismic collapse capacity of public buildings are obtained. The experimental results indicate that the proposed method could exactly describe the seismic collapse capacity of public buildings, thus improving the economic benefits.

    • Study on the Multistage Seismic Response of Long-span Bridge Structures

      2018, 40(1):26-31. DOI: 10.3969/j.issn.1000-0844.2018.01.026

      Abstract (846) HTML (0) PDF 1.57 M (687) Comment (0) Favorites

      Abstract:As a public facility, the seismic performance of long-span bridges has been frequently studied. The seismic excitations that are inputted on the supports of long-span bridge structures are different under earthquakes; consequently, the responses of bridge structures under multistage earthquakes are different. This research analyzes the influence of the radiation wave motion around a bridge pier on the bridge structure under the action of a multilevel earthquake and discusses the pier-water coupling boundary of long-span bridges. Based on the response spectrum theory, the maximum seismic force endured by the long-span bridge structure is calculated, and the multilevel seismic response curve of the structure is obtained. Furthermore, taking a six-span bridge as an example, this research analyzes the response time histories of displacement, sheer force, and bending moment of the bridge under multistage earthquakes and presents some effective conclusions.

    • Elasto-plastic Finite Element Analysis of Typical Brick-Wood Rural Buildings Under Ground Motions

      2018, 40(1):32-40. DOI: 10.3969/j.issn.1000-0844.2018.01.032

      Abstract (883) HTML (0) PDF 16.58 M (995) Comment (0) Favorites

      Abstract:Aiming at brick-wood rural residence that occupies the highest proportion among all rural residences in China, an elasto-plastic analysis on mode and acceleration time-histories of a typical structure is examined by applying ABAQUS software. The first three characteristic periods and vibration modes of two brick-wood rural buildings with masonry strengths of M0.5 and M5 are given, and the results are then compared and analyzed with the value calculated using an empirical formula, proposing the problems and suggestions on empirical formula revisions. In this study, by taking Tianjin seismic waves as the input ground motion, this study calculates the elasto-plastic responses of two different brick-wood rural buildings at different seismic peak accelerations and depicts the corresponding tensile damage nephograms. The damage characteristics and seismic weak part of the structure are also analyzed. The contrastive analysis on different masonry strengths shows that the masonry strength is a key factor affecting the seismic capability of the structure.

    • Simulation and Analysis of the Progressive Collapse of Reinforced Concrete Structures under Multidimensional Earthquakes

      2018, 40(1):41-47. DOI: 10.3969/j.issn.1000-0844.2018.01.041

      Abstract (786) HTML (0) PDF 2.27 M (1123) Comment (0) Favorites

      Abstract:This report establishes a theoretical model of the progressive collapse of reinforced concrete (RC) structures with the discrete element method to improve the seismic performance of RC structures. In addition, this report analyzes the failure mechanism of RC structures subjected to multidimensional earthquakes and the progressive collapse-resisting capability of RC structures under multidimensional earthquakes based on the characteristics of RC buildings and structural joints. In addition, a numerical simulation of the progressive collapse process of the structure is performed. Based on the numerical simulation results, the alternate path method is used, and the anti-progressive collapse analysis of the structure is performed. The simulation experimental results show that the proposed method can accurately determine the progressive collapse-resisting capability of the structure. Under multidimensional earthquakes, the torsional amplitude of the building structure increases, and the divergent behavior of the top displacement is significant. There are different interstory drifts and weak sections at different stories, and the progressive collapse-resisting performance of the structure improves when the failed element is located at a higher level.

    • Impact Analysis Model Simulation for Long-span Cylindrical Support Building Structures under Strong Earthquakes

      2018, 40(1):48-53. DOI: 10.3969/j.issn.1000-0844.2018.01.048

      Abstract (867) HTML (0) PDF 1.67 M (1218) Comment (0) Favorites

      Abstract:Long-span buildings with cylindrical support have poor stability and cannot maintain a stable structural state under strong shock. To solve this problem, this study designs a simulation model for shock analysis of long-span cylindrical support building structures under strong earthquake excitation. Through determining cylindrical analysis rules, analyzing simulations, monitoring finite element support, and performing a bearing capacity analysis of the cylindrical support system, the simulation analysis and monitoring of the model are completed. Consequently, the static analysis of the strong earthquake impact on the long-span building structure is performed, and the structure of the model of a building effected by a strong earthquake is adjusted. Simulation of the strong earthquake impact environment and the experimental results show that the application of analysis and simulation model for large-span cylindrical support building structures effected by a strong earthquake can find the weak points and structural units with poor stability of the long-span cylindrical support structure, thus improving the stability of this kind of buildings effected by of strong earthquakes.

    • Test and Analysis of the Ultimate Bearing Capacity of Residential Building Steel Structures in Seismic Areas

      2018, 40(1):54-59. DOI: 10.3969/j.issn.1000-0844.2018.01.054

      Abstract (801) HTML (0) PDF 1.15 M (1011) Comment (0) Favorites

      Abstract:Traditional methods used to test the ultimate bearing capacity of residential building steel structures are generally based on static test data and have high requirements for several of their components. However, these methods cannot measure hidden components, thus providing low-accuracy test results. Therefore, a method based on vibration parameters and dynamic model updating is proposed to predict and analyze the ultimate bearing capacity of residential building steel structures in a seismic area in this study. The relationship between vibration parameters and the ultimate bearing capacity of building steel structures was analyzed, and the simplified vibration equation was derived to determine the relationship between vibration parameters and limit load. Based on the dynamic model updating theory, the linear buckling method, geometric nonlinear method, and double nonlinear analysis method were adopted to detect the ultimate bearing capacity of residential building steel structures in an earthquake area. The experimental results show that the proposed method is effective in analyzing the hook load and load-deflection relation curve of residential building steel structures. Furthermore, the effect of numerical calculation is good, and the precision of predicted ultimate bearing capacity is high.

    • Research on Energy Saving Technology of Residential Buildings in Pastoral Area under Seven Degree Seismic Fortification

      2018, 40(1):60-65. DOI: 10.3969/j.issn.1000-0844.2018.01.060

      Abstract (886) HTML (0) PDF 2.54 M (618) Comment (0) Favorites

      Abstract:To improve the energy utilization and reduce the energy consumption of buildings, it is important to design residential buildings in pastoral areas with seismic fortification and with an energy saving design. Traditional energy saving technology mainly improves the energy utilization through reducing the energy consumption of buildings; consequently, the energy saving effect is poor and single. This paper uses ANSYS software and the Block Lanczos method to analyze the mode of residential building structures in pastoral areas with seven-degree seismic fortification and to optimize the building energy saving technology by analyzing the material of envelopes, door, and windows of buildings in pastoral areas. The experimental results show that the improved energy saving technology can effectively reduce the energy consumption and improve the energy utilization in the pastoral area of Inner Mongolia.

    • >地震科学研究
    • Characteristics of Present-day Crustal Deformation of Weihe Basin Based on GPS Data

      2018, 40(1):66-72. DOI: 10.3969/j.issn.1000-0844.2018.01.066

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      Abstract:Based on 2001-2015 flow and continuous GPS observation data, the horizontal velocity field model of Weihe basin is established in this study using the Hardy function interpolation method, and the strain characteristic parameters in spherical coordinates were calculated. Based on the geological tectonic background of the Shaanxi area, the distribution characteristics of horizontal velocity field and strain field in the Weihe basin are analyzed. The results show the following:(1) The GPS velocity field in the Western Weihe basin was obviously affected by the combined action of Qinghai-Tibet block and Erdos block, and the GPS velocity field in the western region is larger than that in central and eastern regions, which the GPS velocity field rotates clockwise. (2) The change of main stress field in the Western Weihe basin is complicated, while the change of the main strain in the Xi'an area is obvious, corresponding to the Gaoling MS4.4 earthquake on November 05, 2009. (3) The changes of principal strain, maximum shear strain, and plain strain during 2001-2010 are more obvious than those during 2011-2015, indicating the stress field in the whole Weihe basin has been released and adjusted after the Gaoling MS4.4 earthquake, and the earthquake urgency has been relatively low in the Weihe basin.

    • Fault Slip Tendency in the Western Area of North Tianshan Based on Measured In-situ Stress Data

      2018, 40(1):73-78,91. DOI: 10.3969/j.issn.1000-0844.2018.01.073

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      Abstract:The North Tianshan area is one of the most active areas in the Tianshan Seismic Belt. The investigation of crustal stress state in the area can offer important reliable references to determine the activity and slip tendency of regional faults. The stress data in the North Tianshan area were collected with the hydraulic fracturing and stress relief methods. In this study, the lateral pressure coefficient k, stress accumulative coefficient μm, and fault friction coefficient μ were introduced and utilized to analyze the collected stress data. According to Byerlee's law, the analysis results indicate that the regional stress accumulation is high; the faults in the study area are stable, while some local faults tend to slip. The statistics of earthquakes distribution in the study area indicate that small earthquakes are more likely to occur in the central-western and central-eastern areas where the stress is easy to release, while there are few small earthquakes in the northeastern and northwestern areas, where are inferred as locked patch of stress and likely to occur strong earthquakes because the stress accumulation is high. In addition, the statistics show that the fault zone in the study area is more likely to slip along a NWW-SEE orientation.

    • Current Movement Characteristics of Major Faults in the East Boundary of Sichuan-Yunnan Block

      2018, 40(1):79-85. DOI: 10.3969/j.issn.1000-0844.2018.01.079

      Abstract (722) HTML (0) PDF 13.80 M (1022) Comment (0) Favorites

      Abstract:The Sichuan-Yunnan region located on the southeast margin of the Qinghai-Tibet plateau and east of the stable south China block, has a very complex tectonic setting. A lot of experience was accumulated by using GPS observation data in order to analyze the movement characteristics of the main faults. Based on the GPS observation data in east boundary of the Sichuan-Yunnan block during 2009-2015 and the slip rates of the major faults in the study area were calculated by using the block model and GPS profile method, respectively. Additionally, the recent movement characteristics of the faults were analyzed by combining them with the time series of the regional strain across the fault zone. The results show that, from the GPS perspective of velocity change, the velocity field during the period 2013-2015 in the north-east part of the Sichuan-Yunnan block exhibited an eastbound increase with a very slight change. From the perspective of the slip rate, the sinistral strike-slip movement and the tensile movement in the northern part of the Xianshuihe fault increased. The left-lateral strike-slip movement in the Xiaojiang fault was, in general, slightly enhanced. From the perspective of the regional strain time series after removing the linear trend, the principal tension strain of the southern section of the Xiaojiang fault exhibited a trend reversal at the end of 2014, and this should be investigated further in future work.

    • Characteristics of the Beichuan River Terraces in the North of Lishi Area and Its Neotectonic Indication

      2018, 40(1):86-91. DOI: 10.3969/j.issn.1000-0844.2018.01.086

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      Abstract:The Lvliang Mountain uplift area is located in the west of Shanxi Fault Belt. The extent and the period of the mountain uplift and the river terraces on the mountain have been rarely studied, in particular, after the late Quaternary. In this study, the stratigraphic and geomorphological features of the terraces in the north of Lishi are studied in detail, and the uplift of Lvliang Mountain is also discussed. The river valley of the study area is wide, and the Beichuan River develops on the eastern side of the valley. In addition, the east side is narrower and the west side is wider, which is the main human activity area. The width of the valley is about 0.9~1.6 km, and the elevation difference of the valley is small and the surface is flat. The floodplain and the first and second terraces are also widely distributed in the Beichuan River valley. The third terrace is rarely developed in the area. The first-order terrace and river floodplain formed during the Holocene period, the second-order terrace formed in the Late Pleistocene period, and the third-order terrace formed in the Early-Late Pleistocene period. Meanwhile, the third-order terrace is incomplete, and it has larger height difference than the height difference in the second terrace. The second-order terrace is narrow and the first-order terrace is relatively wide, and the height difference of the two steps is not remarkable. The first-order terrace is relatively wide and the river floodplain is relatively narrow, and the height difference between the two is not significantly big. The results show that the mountain has been uplifted three times intermittently since Late Pleistocene; in addition, the uplift of the mountain is relatively rapid and intense, and the uplift proceeds in a relatively slow process from the Later-Late Pleistocene to the Holocene periods.

    • Late Quaternary Activity Characteristics of Western Piedmont Fault of Gangdeershan in the Wuhai Fault Depression, Inner Mongolia

      2018, 40(1):92-100. DOI: 10.3969/j.issn.1000-0844.2018.01.092

      Abstract (767) HTML (0) PDF 16.50 M (484) Comment (0) Favorites

      Abstract:The western piedmont fault of Gangdeershan is a basin-controlled fault in the Wuhai fault depression. Based on field geological surveys, structural section analysis, and shallow geophysical and geochemical explorations, we analyzed the characteristics of the late Quaternary activity of this fault. Through field geological investigation, fault tracing, and structural profile analysis, we determined that the western piedmont fault of Gangdeershan extends north to south, with the northern end at Guanyinsi, Wuhai city, the southern end at Sandaokan, and further south the presence of a hidden fault. The overall strike of the fault is NNE, the dip angle is 60°~80°, the fault throw is 10~100 cm, and it has both bundle formation and zone formation characteristics. The tectonic activity is strong in the study area, and the elevation difference between the sides of the basin and the mountain is about 400 m. We found the Holocene alluvial sand and gravel deposits to be faulted. The study area is located in the earthquake-free zone and the stress-adjustment transition zone between the northern and southern earthquake areas, and there is a possibility of moderate earthquake activity in the future. Shallow geophysical and geochemical explorations also reveal obvious abnormal changes in the location of faults, and confirm the existence of the fault. The shallow geophysical exploration results show obvious stratigraphic position change and the fault characteristics of bundle formation and zone formation. In addition, most of the faults are high-angle normal faults, and the faults tend to be western. Geochemical surveys mainly employ two methods:soil radon and soil mercury analysis. Based on the above results, we consider the western piedmont fault of Gangdeershan to be a Holocene active fault characterized by tension.

    • >土动力学与震灾机理
    • Study on the Dynamic Characteristics of Remolded Loess in Shanxi Expressway Subgrade under Vehicle Loads

      2018, 40(1):101-104. DOI: 10.3969/j.issn.1000-0844.2018.01.101

      Abstract (1027) HTML (0) PDF 2.29 M (936) Comment (0) Favorites

      Abstract:To determine the effects of vehicle load on the soil mass of an expressway subgrade soil in Shanxi Province, we investigated the dynamic response from vehicle loads, the seismic waveforms, and the soil dry density and confining pressures. The results show that the volume deformation of the subgrade soil increased with an increase in waveform ratio and vehicle load, the dynamic elastic modulus increased with an increase in dry density and confining pressure, and the damping ratio decreased with an increase in confining pressure.

    • Anti-liquefaction Properties of Saturated Loess Improved by Fly Ash

      2018, 40(1):105-110. DOI: 10.3969/j.issn.1000-0844.2018.01.105

      Abstract (641) HTML (0) PDF 3.55 M (648) Comment (0) Favorites

      Abstract:To economically reduce seismic liquefaction damage to saturated loess foundations, variations in the characteristics of dynamic stress, dynamic strain, and dynamic pore water pressure are analyzed using dynamic triaxial tests on improved saturated loess with different dosages of fly ash. The law of influence of this dosage on the liquefaction stress ratio, dynamic residual deformation, and dynamic pore water pressure of the improved loess is then studied. Combined with microscopic test results, the physical-chemical anti-liquefaction mechanism of saturated loess improved by fly ash is also discussed. Results show that the dosage of fly ash has a significant influence on the liquefaction stress ratio, dynamic strain, and dynamic pore water pressure of the improved loess. With an increase in the dosage, there is a respective increase in the liquefaction stress ratio of the improved loess:after the dosage reaches 15%, there is an evident increase in the liquefaction stress ratio with a continued increase in the dosage. In addition, the dynamic strain and dynamic pore water pressure of the improved loess increase with a decrease in the fly ash dosage:after the dosage reaches 25%, the saturated improved loess cannot be liquefied. Scanning electron microscope (SEM) results indicate that the physical-chemical anti-liquefaction mechanism of saturated loess improved by fly ash is mainly related to the hydration process of the fly ash with respect to the filling effect of the colloid product and particles and adsorption of free water by fly ash.

    • Risk Assessment of Secondary Geological Disasters Induced in an Earthquake-Stricken Area

      2018, 40(1):111-115. DOI: 10.3969/j.issn.1000-0844.2018.01.111

      Abstract (736) HTML (0) PDF 3.77 M (1180) Comment (0) Favorites

      Abstract:This paper shows the relevance of an earthquake-stricken area and secondary geological disasters based on the analysis of secondary geological disaster types and harms, and taking an earthquake disaster area as an example, the total value and discharge of debris flow in the area are calculated to determine the risk of debris flow. The vulnerability index is introduced to determine the vulnerability of secondary mountain hazard of each assessment unit. Combined with the actual situation of the studied area, an evaluation model for determining the risk of secondary geological disasters is established based on analytic hierarchy process, and the model can be used to evaluate the risk of secondary geological disasters induced in earthquake disaster areas. Taking the disaster risk triggered by debris flow as an example, an experimental study is performed, and the results indicate that the proposed method in this paper can effectively determine the location of secondary geological disasters induced in the earthquake disaster area. However, the risk assessment of secondary geological disasters induced by longitudinal earthquakes much be studied further.

    • Seismic Disaster Mechanism of Owner-built Frame Structures in Zhangmu Town During Nepal Earthquakes

      2018, 40(1):116-123. DOI: 10.3969/j.issn.1000-0844.2018.01.116

      Abstract (843) HTML (0) PDF 13.11 M (1157) Comment (0) Favorites

      Abstract:In 2015, Nepal suffered four M>7 earthquakes that had a considerable impact on parts of Tibet, China. Since the town of Zhangmu is an important trading port for China and Nepal, a large number of Nepal-type self-built RC frame structures are built in this region. By investigating earthquake damaged frame structures, in combination with their special construction methods and structural characteristics, the earthquake resistant capacity of these structures was analyzed. Moreover, the seismic damage law and disaster mechanism of the frame structures under the effect of earthquakes was investigated. The results showed that, in addition to being economical, the owner-built frame structures have a high utilization ratio of component carrying capacity. However, their safety reserve is low. The seismic failure mode of this type of structure is mainly due to the failure of frame columns and the cracking of filling walls. The destruction of the roof is mainly caused by secondary geological disasters, such as the falling of mountain rocks, which is caused by earthquakes. Therefore, the location of a house should take full account of the influence of geological disasters to the construction site. The number of floors is immensely influential with regard to earthquake damages suffered by this type of structure; thus, a suitable number of floors is 1~7. The seismic performance of such structures is superior; therefore, it is suitable for widespread application, including application to low intensity areas in China. The results of this study can be used as a guide for earthquake resistant planning and construction of owner-built houses in Chinese villages and towns.

    • A Comparison and Analysis of Instrumental Intensity and Macroseismic Survey Intensity of the 2013 Minxian-Zhangxian MS6.6 Earthquake in Gansu Province

      2018, 40(1):124-129. DOI: 10.3969/j.issn.1000-0844.2018.01.124

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      Abstract:On July 22, 2013, an MS6.6 earthquake occurred at the border area between Minxian and Zhangxian Counties, Gansu Province. In this study, 117 groups of three-component acceleration records collected by the Northwestern Strong Motion Networks Center were processed and analyzed, and the resultant instrumental intensity values were calculated and analyzed. The instrumental intensities and the intensities obtained from the Minxian-Zhangxian seismic intensity map (China Earthquake Administration, 2013) were compared and analyzed, and the stations with deviations less than 1 degree were determined to account for 81.8%. The instrumental intensities and the intensities of surveying points within 5 km around the stations were also compared, and the stations with the same intensity account for 50%. The disaster investigation and analysis indicate that most buildings in the Minxian-Zhangxian earthquake-stricken area are of civil and wood structures, and they are more heavily damaged than other regions that experienced the earthquake at the same intensity. Although the instrumental intensity is not quite consistent with the microseismic intensity, the instrumental intensity reflects the earthquake disaster to a certain extent and provides the basis for determining emergency rescue.

    • >地震观测
    • Analysis of Recorded Waveform During the 8·12 Explosion Incident in Tianjin Harbor

      2018, 40(1):130-138. DOI: 10.3969/j.issn.1000-0844.2018.01.130

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      Abstract:This study conducts a preliminary analysis of waveform data from a series of explosive events that occurred in Tianjin harbor on August 12, 2015, which were recorded by 23 short-period seismometers of the China Seismograph Network in Tianjin. Four explosive events were identified using the envelope method and wave matching method, and their locations were determined by applying the master event location algorithm. Analysis results show that the first explosion occurred at 23:34:04 on August 12, 2015, and a larger blast then occurred after 1.77 s. The third event was the largest and occurred 34.11 s after the first event, and the last explosion occurred 86.33 s after the first. The second and third explosions occurred 65~70 m apart, and the second explosion was 160~170 m from the fourth. This paper also compares waveform data of explosions, mine collapse, nuclear explosion, and a natural earthquake in the time and frequency domains, respectively, and results show that there are strong differences between the seismic phase characteristics of these events.

    • Strong Motion Records and Its Characteristics in Alashanzuoqi MS5.0 Earthquake on June 3, 2017, Inner Mongolia

      2018, 40(1):139-145. DOI: 10.3969/j.issn.1000-0844.2018.01.139

      Abstract (937) HTML (0) PDF 8.32 M (1014) Comment (0) Favorites

      Abstract:A MS5.0 earthquake occurred on June 03, 2017 in Alashan County, Inner Mongolia. During the earthquake, 150 three-component acceleration records of the main shock were obtained from 50 strong motion seismographs in Gansu Strong Motion Network. Based on these records, we first calculated the distribution of peak accelerations around the epicenter. The basic characteristics of this earthquake were analyzed according to the acceleration time-history curves and acceleration response spectra recorded by four typical stations. Further, the attenuation relation between PGAs and spectral accelerations with different distances were analyzed by comparing the observed data with Italy 08-ground motion prediction equations. The spectral ratio curves were calculated based on strong motion data from the four stations. It was found that by comparing the spectral ratio results with the borehole information from these four stations, the spectral ratio method could accurately reflect the actual site situation.

    • Simulation Analysis of Influence of Stress Field in Surrounding Rocks of Chambers on Ground Tilt Observation

      2018, 40(1):146-152. DOI: 10.3969/j.issn.1000-0844.2018.01.146

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      Abstract:In the early stages of underground chamber formation, where the earthquake observation instruments are located, the chamber floor will exhibit the phenomenon of floor heave. Being a slow process, it will seriously affect the long-time change of ground tilt observation, and thus cause misjudgment in earthquake monitoring. In this study, through the numerical simulation of an underground stress chamber, we propose a stress field distribution law in the surrounding rocks of the chamber, which is obtained in the Z-direction deformation values of the grid nodes at the chamber floor. Then these deformation values are converted to tilt observation data. The results show that the change of the maximum principal stress field at the chamber floor will affect the horizontal pendulum of the seismograph. The tensile stress field varies at different degrees with different instrument positions. This irregular gradient tensile stress change in the vertical direction leads to the floor heave phenomenon, which results to the change of ground tilt in the chamber. The influence range of the ground tilt is between 17.46 and 8 177.02/10-3″ arc-seconds. This study can help in meeting floor support requirements and the basis for a newly-built chamber, in order to better serve earthquake research in China.

    • Study on Correlation of Volume Strain Observation Based on Borehole Features

      2018, 40(1):153-158. DOI: 10.3969/j.issn.1000-0844.2018.01.153

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      Abstract:Fifteen volume strain observation points were established in Jiangsu province during the construction of the Jiangsu digital seismic precursor network. However, the stability of observation data obtained from these points is influenced by differing installation times, geographical positions, geological conditions, and drilling features. Regression and harmonic analyses have been used in this study to discuss the observed data of volume strain in Jiangsu province; further, the variation characteristics of observed data obtained from different stations have also been analyzed. In combination with borehole histogram and the running status of instruments, the relation among the tidal factor of the M2 wave, regression coefficients of pressure and water level, lithology, and borehole features are analyzed. In addition, effective measures that can improve the quality of volume strain observation are discussed.

    • >其他
    • Vibration Isolation Measures of High Precision Equipment Platform Foundation

      2018, 40(1):159-165. DOI: 10.3969/j.issn.1000-0844.2018.01.159

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      Abstract:The study of vibration isolation for a foundation platform is of great practical significance to high precision equipment. In this study, along with the vibration isolation project for the foundation of a high precision equipment platform, a 3D finite element method is presented for foundation vibration isolation analysis by considering the foundation-ground-foundation interaction, on the basis of User Programmable Features (UPFs). The dynamic machine, its surrounding ground, and the high precision equipment platform foundation are taken as an integrated coupling object. A 3D compact viscous-spring boundary was constructed, which can simulate not only the radiation damping of semi-infinite soil, but also the elasticity recovery capacity of the far field media on the boundary. The boundary was implemented with the ANSYS software. Then, the rationality of the model was verified by comparing the vibration attenuation curves obtained from the regression analysis by using the least squares method with the results of the numerical simulation. Finally, according to ground conditions, the finite element models, which take different vibration isolation measures were established, and the damping effect of isolation trenches with different influence factors were analyzed. The calculation results indicate that the location, depth, and length of vibration isolation trench were important factors in practical projects, and that a reasonable selection of these factors would obtain a better vibration isolation effect.

    • Measurement and Field Test Research on Vibration Acceleration of Dynamic Compaction

      2018, 40(1):166-170. DOI: 10.3969/j.issn.1000-0844.2018.01.166

      Abstract (1204) HTML (0) PDF 1.77 M (694) Comment (0) Favorites

      Abstract:As a kind of foundation treatment method, dynamic compaction can quickly improve the bearing capacity and compressive modulus of foundations, with characteristics such as short duration, good effect, and low cost. However, the huge vibration waves caused by dynamic compaction tend to affect the stability of surrounding buildings and slopes. Therefore, it is of great theoretical and practical significance to study the propagation law of dynamic compaction vibration waves. In this study, combined with the monitoring scheme of a terrain design used in a dynamic compaction foundation project in the Yan'an New Area, we selected a site in the filling area in order to conduct field tests on the vibration acceleration of dynamic compaction. Based on these field tests, the propagation law of dynamic compaction vibration waves along the horizontal and the slope directions, respectively, were analyzed, and the effect of the energy level on the vibration acceleration was discussed. The results show that both the radial and vertical acceleration values of the vibration waves decrease with the increase of distance from the tamping point. At the same distance from the tamping point, the vertical and radial acceleration values along the horizontal direction were greater to those along the direction of the ramp. With the increase of energy level, the dynamic compaction waves were enhanced, and then both the radial and vertical accelerations at the same distance from the tamping point increased significantly.

    • Design Study for Embed Depth of the Supporting Pile in the Pile-Anchor Supporting System of a Foundation Ditch

      2018, 40(1):171-177. DOI: 10.3969/j.issn.1000-0844.2018.01.171

      Abstract (876) HTML (0) PDF 1.04 M (1466) Comment (0) Favorites

      Abstract:In the design of a pile-anchor supporting system of a foundation ditch, adequately designing the embed depth of the supporting pile is very important. Generally, a deterministic model of the simple arc sliding strip method is used to calculate the overall stability of the foundation ditch, which is a constant value. As the uncertainties of loads and soil properties are not considered, the actual overall stability may exceed the calculated result. In this paper, first, based on a typical pile-anchor supporting system of a foundation ditch, the deterministic model of the simple arc sliding strip method is introduced to calculate the overall stability. Based on the deterministic model, the limit state equation and reliability model of overall stability for the pile-anchor supporting system of a foundation ditch is developed by considering the loads and the soil parameters as independent normal distribution variables. In addition, the reliability index of overall stability is calculated using the first order reliability method. The target reliability index is used to determine the embed depth of the supporting pile. Finally, through a specific pile-anchor supporting system of a foundation ditch, the safety factor and reliability index of the overall stability supporting pile were calculated using the safety factor method and reliability method, respectively, to determine the embed depth of the supporting pile. Also, the influence of coefficient of variations of calculating the parameters for the reliability index of the overall stability is analyzed. Through this study, it can be known that the embed depth of the supporting pile designed using the deterministic method may damage the foundation ditch. The embed depth of the supporting pile designed using reliability analysis is more safe, reasonable, and economical since the uncertainties of the loads and soil properties are considered. Besides, the variation of parameters c, φ, and qs has obvious influence on the reliability index of the overall stability and pile length. Therefore, when designing the embed depth of the supporting pile in a foundation ditch, reliability analysis should be used together with the simple arc sliding strip deterministic method.

    • Analysis of Characteristics of Horizontal Rotation-invariant Mean Duration

      2018, 40(1):178-187. DOI: 10.3969/j.issn.1000-0844.2018.01.178

      Abstract (857) HTML (0) PDF 10.06 M (723) Comment (0) Favorites

      Abstract:Determining ground motion duration is an important factor in the seismic analysis of structures as it has a significant impact on low-ycle fatigue, the cumulative effect of damage, and the inelastic failure of structures. In this paper, after determining the significant and Bolt durations, we introduce the concept of rotation-invariant mean duration. Then, based on Wenchuan seismic records, we discuss the spatial variability law of rotation-invariant mean duration with changes in the fault distance. Lastly, we analyze the ratio of the rotation-invariant mean duration and record-based duration of the measuring points as well as their correlation. The results indicate that the rotation-invariant mean duration is not equal to the single record-based duration. The rotation-invariant mean energy duration and relative Bolt duration increase with increased fault distance, whereas the rotation-invariant mean absolute Bolt duration decreases with increased fault distance. The rotation-invariant mean duration and record-based duration are highly correlated. By comparing different definitions of duration, we found that the correlation between rotation-invariant mean duration and a record-based duration of 90% energy is stronger than that of 70% energy. Furthermore, the correlation with the absolute Bolt duration is more significant than that with the relative Bolt duration, and the correlation with energy duration is more significant than that with the Bolt duration.

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